Apparatus and methods for selectively deactivating one or more combustion valves in an internal combustion engine are well known. Such devices, known in the art as variable valve deactivation or activation (VVA) devices, may take the form of, for example, a selectively latchable rocker arm, a roller finger follower, a rocker arm support member such as a hydraulic lash adjuster, or a hydraulic lifter. VVA is also known in the art as “cylinder deactivation” because the effect of deactivating either or both of the intake and exhaust valves of a cylinder is to remove that cylinder as a driving element of the engine. Such deactivation can improve the fuel efficiency of a multiple-cylinder engine under load conditions wherein the power capacity of the entire engine is not needed.
Valve deactivation may be applied to as few as one cylinder; however, as commonly practiced in the automotive arts, an entire bank of cylinders in a multiple-bank engine is deactivated as a unit. For example, in a V-6 engine, an entire bank of three cylinders may be deactivated, permitting the engine to continue to run on the other three-cylinder bank as a three-cylinder engine until the full engine capacity is again required.
When the intake and exhaust valve trains of a bank are both deactivated, the fuel injectors and spark ignitors (for spark-ignited engines) are also deactivated. Each piston in the deactivated bank continues to compress and expand a captive air supply in lost motion, but there is no net work performed and no flow of air or fuel through the cylinder.
It is known that deactivation mechanisms can fail, resulting in the valves' continuing to open and close. Such failure results in a significant reduction in fuel economy and in loss of thermal and compositional control of the exhaust stream, which can have serious adverse consequences on functions such as exhaust gas recirculation (EGR) and emissions control. Therefore, it is important to detect immediately when a valve deactivation mechanism fails.
What is needed in the art is a method and apparatus for detecting failure of a valve deactivation mechanism.
It is a principal object of the present invention to detect and alarm as soon as possible any failure of a valve deactivation mechanism in an internal combustion engine.